Salts of the b11h14-anion

ABSTRACT

METAL SALTS OF THE B11H14- ANION FORMED BY REACTING DECABORANE WITH A METAL BOROTETRAHYDRIDE AT TEMPERATURES OF AT LEAST 45*C. AND AMMONIUM SALTS OF THE B11H14ANION FORMED BY THE METATHETICAL REACTION OF METAL B11H14- SALTS WITH THE APPROPRIATE AMMONIUM SALTS. THE B11H14- SALTS OF THE INVENTION ARE USEFUL AS COMPONENTS OF HIGH ENERGY FUELS.

Nov. 13, 1973 v. D. AFTANDILIAN SALTS OF THE BHHM ANION 3 Sheets-Sheet l Filed May 20. 1969 I N VEN TOR Nov. 13, 1973 vv. D. AFTANDILIAN SALTS OF THE 8Min" ANION 5 Sheets-Sheet 2 Filed May 2U, 1969 ogm Nov. 13, 1973 v. n. AFTANDILIAN SALTS OF THE BIHH--ANION 3 Sheets-Sheet 3 Filed may 2o, 1969 "United States Patent O U.S. Cl. 423-286 Claims ABSTRACT OF 'I'HE DISCLOSURE Metal salts of the BHHM" anion formed by reacting decaborane with a metal borotetrahydride at temperatures of at least 45 C. and ammonium salts of the BHHM- anion formed by the metathetical reaction of metal B11H14 salts with the appropriate ammonium salts. The BHHM'* salts of this invention are useful as components of high energy fuels.

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of my application, Ser. No. 20,835, filed Apr. 8, 1960, now abandoned, and a division of my copending application, Ser. No. 245,463, tiled Dec. 18, 1962, issued as U.S. Pat. 3,458,531 on July 29, 1969.

This invention relates to ionic boron compounds. More particularly, it relates to novel boron hydride salts and to methods for their preparation.

Boron compounds a're becoming of increasing value in various applications such as high energy fuels and reducing agents. It is therefore a desirable goal to provide new boron compounds which are especially useful in these and other applications.

The present invention provides a novel group of salts of the boron hydride anion B11H14. The salts of this invention have the general formula wherein M is a cation selected from the group consisting of metals having a standard oxidation potential of at least 0.5 volt and an atomic number less than 57, ammonium radicals of the formulas R2H2N+, R3HN+, R.,N+, sulfonium radicals of the formula R3S+, and phosphonium radicals of the formula R4P+, R is selected from the group consisting of alkyl radicals, and n, the valence of the radical M, is an integer greater than 0 and less than 5, i.e., l, 2, 3, or 4. The oxidation potentials referred to herein are those listed on p. 1733 of Handbook of Chemistry and Physics, 41st ed., Chemical Rubber Publishing Co. (1959).

The alkali and alkaline earth metals, i.e., the elements of Groups I-A and II-A, respectively, of the Periodic Table having atomic numbers between 3 and 56, inclusive, include lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, and barium. These form a preferred group of metal cations in the salts of this invention. Other cations of metals having standard oxidation potentials of at least 0.5 and atomic numbers less than 57 include scandium, aluminum, titanium, zirconium, manganese, vanadium, niobium, zinc, chromium, and gallium. The Rs in the above formulas for the ammonium, sulfonium and phosphonium compounds can be either the same or different and preferably contain up to 18 carbons each. It will be appreciated that when M inthe above formula is an alkali metal or an ammonium, sulfonium or phosphonium radical, n is 1; when M is an alkaline earth metal, n is 2; and when M is another metal of the above-defined type, n can be 2, 3 or 4.

3,772,426 Patented Nov. 13, 1973 rice The salts of this invention are soluble in water with slow decomposition in such solutions. Some of the salts are also soluble in ethers, but all are insoluble in hydrocarbons. Both the aqueous and ethereal solutions of the salts are very strong reducing media, e.g., they are capable 0f reducing silver and nickel salts to the corresponding free metals. These salts of the BHHM anion are also hypergolic with nitric acid, i.e., they are ignited by Contact with concentrated nitric acid.

The alkali and alkaline earth metal salts of this invention can be prepared by the reaction of decaborane with an alkali metal or alkaline earth metal borohydride in an ether. The reaction is illustrated by the following equation:

In this equation the symbol M represents an alkali or alkaline earth metal of valence n. When M' is an alkali metal, n is 1, and when M is an alkaline earth metal, n is 2.

From Equation 2 the stoichiometric proportions of decarborane and metal borohydride required in this reaction are one mole of decaborane for each BH4'- ion in the metal borohydride. Thus, one mole of alkali metal borohydride is required for each mole of decaborane and one mole of alkaline earth metal borohydride is required for every two moles of decaborane.

The ether employed as a reaction medium in this process of making metal salts of the invention can be any organic compound which contains at least one moiety and is inert towards reactants and reaction products. One useful class of ethers thus comprises those compounds in which two identical or dilferent hydrocarbon radicals are joined by au atom of oxygen. Examples of specific operable ethers include alkyl ethers, e.g., diethyl ether, methyl ethyl ether, di-n-butyl ether; cyclic ethers, e.g., tetrahydrofuran and dioxane; ethylene glycol ethers, e.g., ethylene glycol dimethyl ether (glyme), diethylene glycol dimethyl ether (diglyme) and triethylene glycol dimethyl ether (triglyme). Best results are obtained when dioxane, glyme or diglyme are used as the reaction medium; consequently, these are the preferred reaction media. The amount of ether employed should be at least an amount equal to the total weight of the reactants. Proportions of ether reaction medium ranging from 10 to 40 times the total weight of the reactants give very good results.

Reaction temperatures of at -least about 45 C. are used in this process. Metal salts of the BHHMh anion are not obtained at temperatures of 25 C. or lower. The critical nature of the minimum operating temperature of 45 C. is shown by the fact that NaB10H13 is the only salt formed when the reaction of sodium borohydride with decarborane in au ether is carried out at 25 C. or lower (see U.S. Pat. 2,993,751 and Hawthorne et al., I. Am. Chem. Soc., 82, 1825 (1960)). However, when the NaB10H13 salt obtained at 25 C. is heated with diborane at 45 C. in the presence of an ether NaBuHM is formed. Reaction temperatures ranging from 45 C. up to, say, about C. are generally operable. Preferably, the reaction is carried out at temperatures between 65 and 100 C. It is convenient to use a temperature at which the ether reaction medium boils at atmospheric pressures.

The pressures under which the reaction is carried out are not critical. Subatmospheric, atmospheric, and superatmospheric pressures are all operable. When low-boling ethers are employed, it is convenient to use a closed reaction vessel and the autogenous pressure developed by the reaction system at a reaction temperature. When an ether boiling between 65 and 100 C. is employed, it is convenient to carry out the reaction under reflux conditions at atmospheric pressure. Similarly, when high boiling ethers are employed, it is often convenient to use subatmospheric reaction pressures.

The reaction between the metal borohydride and the decarborane is continued until evolution of hydrogen ceases. Several hours are generally required to complete a reaction. The exact time depends mainly on the particular metal borohydride used, the particular ether, and the particular reaction temperature being employed. With lithium and sodium borohydrides and reaction media such as dioxane or glyme, reaction temperatures of 90- 100 C. require 10-16 hours for completion of the reaction.

The metal salts of the BHHM- anion can be isolated by various methods. The salts prepared as described above are normally obtained in the form of their etherates in which the metal salt is combined with several molecules of ether of crystallization. When the reaction is carried'out in dioxane, the reaction product is a solid dioxanate which can be filtered from the reaction medium and dried at ordinary or moderately elevated temperatures, e.g., temperatures up to 100 C. and preferably under reduced pressure, e.g., pressures as low as a few millimeters of mercury. When ethers other than dioxane are employed as reaction media, the salts obtained are in the form of oils and the salts can be precipitated as the dioxanates by the addition of dioxane to the crude reaction mixtures or to reaction mixtures which have been concentrated by evaporation of excess solvent. The precipitate dioxanate is then filtered and dried as described previously.

Dioxane-free salts of BHHM- can be prepared by dissolving the dioxanate of the BHHM- salt in from two to ten times its weight of water and then evaporating the resulting solution. It is convenient to carry out the evaporation under reduced pressure at slightly above room temperature (e.g., 40 C.). This removes the dioxane and leaves an aqueous solution of the BnHlf salt, e.g., NaBnHM, free of dioxane as shown by infrared analysis. Evaporation of this solution to dryness yields a solid hydrate of NaB11H14. This hydrate can then be dehydrated by conventinal means.

Dioxane-free rnetal salts of BHHM- can also be prepared |by other means. For example, addition of one equivalent of aqueous lithium hydroxide to (CH3 aNHBnHm,

followed by evaporation of the resulting solution to dryness, gives LiBuHM. Another way of obtaining sodium or lithium salts of BHHM- free of ether of crystallization involves passing an aqueous solution of CsBuHM through a column of a strong acid ion exchange resin such as that known commercially as Amberlite IR 140, sodium form, to give an aqueous solution of NaBuHM. This aqueous solution can then be evaporated to dryness leaving a solid hydrate of NaBuHM. Other forms of the Amberlite IR 140 will yield other salts of BuHlf.

The ammonium, sulfonium, and phosphonium salts and some of the metal salts of the BHHM- anion of this invention can be prepared by adding to a first aqueous solution of a soluble salt of a metal or an ammonium, sulfonium, or phosphonium radical with a non-oxidizing anion other than the BuHM" anion, a second aqueous solution containing a B11H14- salt of a metal other than that in the 'first solution, the particular metals being chosen so that the desired salt of the BHHM- anion is relatively insoluble in water compared with starting salt reactants and other reaction products. When aqueous solutions of tetraethylammonium chloride, triethylsulfonium iodide, tributylphosphonium iodide, or cesium chloride, are mixed with aqueous solutions of NaBnHM, the less soluble tetramethylammonium, triethylsulfonium, tributylphosphonium, and cesium salts of the BHHM- anion precipitate from the reaction mixtures. In some cases it is desirable to cool the reaction mixture to complete precipitation of the desired salt. The precipitated salts obtained in this manner do not contain ether of solvation and can be isolated by filtration followed by washing with small amounts of water and drying at moderately elevated temperatures under reduced pressure.

Water-soluble salts of the BHHM- anion are also prepared by a metathetical reaction. Addition of a sulfate of a desired cation M, e.g., aluminum, to an aqueous solution of Ba(B11H14)2 causes precipitation of insoluble barium sulfate leaving an aqueous solution of the desired salt of the BHHM- anion, e.g., the aluminum salt. The barium sulfate is removed by filtration and the filtrate is evaporated to leave the desired salt, e.g., Al(B11H14)3. Diand trivalent metal s-alts of the BHHM- are often isolated as their hydrates. In some cases the water of hydration can be removed by heating under reduced pressure.

The products and processes of this invention are illustrated in further detail in the following:

EMBODIMENTS OF THE INVENTION Example 1 (A) Preparation of NaB11H142.5C4H8O2.-A sample of 0.95 g. of sodium borohydride (0.025 mole) is placed in a 500 ml. 3-necked glass reaction flask equipped with a dropping funnel, a stirrer, and a condenser placed so that condensed vapors are returned to the flask. The flask is filled with nitrogen and is maintained in an atmosphere of nitrogen throughout the run. One hundred milliliters of dry dioxane is introduced into the flask, the mixture is stirred and a solution of 3.80 g. of decaboane (0.031 mole) in ml. of dry dioxane is added dropwise to the reaction mixture. A yellow solid forms and this is accompanied by the evolution of hydrogen. The flask is heated to the lboiling point of the dioxane (100 C.) and the reaction mixture is retluxed for a total of 16 hours at the end of which time evolution of hydrogen has completely stopped. The reaction mixture is cooled and filtered in a stream of nitrogen. The yellow solid precipitate is vacuum-dried at 40 C. and ca. 1 mm. of mercury. There is obtained 7.36 (78% of theory) of NaB11H14-2-5C4H8O2, a compound which can be termed sodium tetradecahydroundecaborate(1-) having 2.5 molecules of dioxane of crystallization.

Analysis.-Calcd for NaB11H14-2.5C4H8O2 (percent): Na, 6.11; B, 31.62; C, 31.91; H, 9.11. Found: Na, 6.6; B, 31.06; C, 31.36; H, 9.10.

Infrared analysis confirms the presence of dioxane in the product, dioxane absorption bands at 7.7, 7.9, 8.9, 9.25, 9.5, 11.1, 11.25, 11.3 and 11.4 microns being present. The infrared spectrum also shows a sharp peak at 3.95 microns which is assigned to the B-H function.

This sodium salt is extremely hygroscopic. It is soluble in diethyl ether and in acetone at room temperature (20- 30 C.), and is insoluble in hydrocarbons, e.g., pentane, hexane, and petroleum ether. When an ether solution of this salt is added to an alcoholic solution of silver nitrate, a precipitate of metallic silver forms immediately. This sodium salt of the BUHM* anion explodes when it is brought in contact with concentrated nitric acid. This salt decomposes slowly in water, e.g., in 24 hours at room temperature.

Acetone solutions of NaB11H14-2-5C4H8O2 are stable at room temperature; however, at moderately elevated temperatures this salt reduces acetone to isopropyl alcohol. For example, a solution of NaBnH14-2.5C4H8O2 in acetone is heated in a sealed glass tube at 55 C. for 64 hours, and the reaction mixture is then hydrolyzed with water. By gas chromatographic and mass spectrometric analyses of the volatile products obtained, it is shown that the acetone is reduced to isopropyl alcohol.

(B) Preparation of dioxane-free NaB11H14.-A sample of the NaB11H14-2-5C4H302 of part (A) of this example is dissolved in about ten times its weight of water and the resulting solution is evaporated under reduced pressure at slightly above room temperature to about 1A@ its original Volume. During the evaporation the dioxane is removed and the residue is an aqueous solution of NaBuHM. Infrared absorption analysis of this aqueous solution shows none of the absorption bands of dioxane at 7.7, 7.9, 8.9, 9.25, 9.5, 11.1, 11.25, 11.3, and 11.4 microns but still shows the sharp peak at 4.0 microns due to B-H and a wide absorption band at 9.7 microns characteristic of the BHHM- anion. The spectrum also shows water absorption bands at 2.7 and 6.2 microns. The complete infrared absorption spectrum of this aqueous solution of NaBnHM is shown in FIG. 1. In this spectrum the absorption peaks at 3.5, 6.9, and 13.9 microns are produced by the polyethylene bags which were used as containers for the aqueous NaB11H14 solutions.

(C) Preparation of NaBuHl., from NaBH13.-A solution of 9.2 millimoles of NaBmHls, prepared as described in US. Pat. 2,993,751 or by Hawthorne et al., J. Am. Chem. Soc. 82, 1825 (1960), in 12 ml. of diethylene glycol dimethyl ether (diglyme) in a vacuum train reaction flask is stirred with 14.5 millimoles of diborane at 45 C. for 2.5 hours, and at room temperature (25 C.) overnight. Careful fractionation of the reaction mixtures gives 6.5 millimoles of unchanged diborane and much hydrogen. The solvent is removed under reduced pressure and there is obtained a yellow solid residue which is an etherate of NaBuHM. This solid is dissolved in water and to the resulting solution is added aqueous tetramethylammonium chloride which gives a precipitate of (CHSMNBHHM. This precipitate is recrystallized from water in the form of pure white crystals. This product is shown to be identical to the product of Example 3 below by its infrared absorption spectrum.

Example 2 Preparation of LiB11H14'2C4H8C2.-A 100 ml. stainless steel reaction vessel is charged with 1.78 g. of decaborane (0.0145 mole) and 0.32 g. of lithium borohydride (0.0145 mole). The reactor is cooled by a bath of a mixture of solid carbon dioxide and acetone and is then evacuated. Thirty milliliters of freshly distilled 1,2-dimethoxyethane (glyme) is introduced into the reactor after which it is closed and heated for 10 hours at 90 C. The reactor is connected to a Vacuum train, opened and the uncondensable gases collected and measured, 0.0270 mole of gas being obtained (93% of theory). Mass spectrometric analysis shows that the gas is 98.2% hydrogen, about 0.7% nitrogen and/or carbon monoxide, and about 0.5% methane. The reaction vessel is opened and its contents filtered. To the yellow filtrate is added 200 ml. of dry dioxane and a yellow precipitate forms immediately. This precipitate is dried in a current of nitrogen at 25 C. There is obtained 3.41 g. (73% of theory) of yellow solid LiB11H14-2C4H8O2, a compound which can be termed lithium tetradecahydroundecaborate(1) having two molecules of dioxane of crystallization. A sample of this material is purified by extraction with dioxane in a Soxhlet extractor. The dioxane-insoluble portion is analyzed.

Analyss.--Calcd for LiB11H14-2C4H8O2 (percent): Li, 2.19; B, 37.63; C, 30.38; H, 9.86. Found (percent): Li, 2.0; B, 38.33; C, 30.10; H, 9.36.

The infrared absorption spectrum obtained on this compound is very similar to that obtained on the sodium salt of Example 1. The spectrum shows the presence of dioxane and the characteristic 3.95 micron band of the B-H function.

The lithium salt of the BHHM anion is extremely hygroscopic. It is soluble in diethyl ether and in 1,2-dimethoxyeth'ane and is insoluble in hydrocarbons (pentane, hexane, and petroleum ether). An ether solution of this salt reduces alcoholic silver nitrate to elemental silver. The salt is ignited -by contact with` nitric acid.

Example 3 Preparation of (CH3)4NB11H14.-The dioxanate of NaBuHM (the product of Example 1) is dissolved in Water and an aqueous solution of tetramethylammonium chloride is added to it. A yellow precipitate forms immediately. The yellow precipitate is ltered from the reaction mixture and dried at 40 C., ca. 1 mm. mercury. Infrared analysis of this product indicates that it does not contain any water or dioxane of solvation. The infrared absorption spectrum shows the charactertistic B-H absorption at 3.95 microns and the tetramethylammonium, (CH3)4N+, absorption at 10.5 microns. This compound can be named tetramethylammonium tetradecahydroundecaborate( 1") Analysz's.-Calcd for C4H26NB11 (percent): C, 23.18; H, 12.64. Found (percent): C, 23.13; H, 10.70.

Example 4 Preparation of CsB11H14.-The addition of an aqueous solution of cesium chloride to an aqueous solution of NaB11H14-2-5C4H8O2 (the product of Example l) gives a bright yellow precipitate. This precipitate is filtered from the reaction mixture, dried at 25 C. and ca. 1 mm. mercury and the product is analyzed by infrared spectroscopy. The infrared absorption spectrum contains a band at 4.05 microns assigned to the B-H function. The spectrum shows no indication of the presence of water or of dioxane. This product can be termed cesium tetradecahydroundecaborate 1- Analyss.-Calcd for CsBuHm (percent): B, 44.7; H, 5.3; Cs, 50.0. Found (percent): B, 44.4; H, 5.4; Cs, 50.4.

By single crystal X-ray analysis, a unit cell of the crystal of CSBHHM is found to have the following dimensions: a=7.35 A., b=11.38 A., c=12.85 A. There are four formula weights per unit cell. The density of the crystals is found to be 1.66. Thus, the experimental formula weight is 265 which is in good agreement with 266 required for CsBuHM.

Example 5 Preparation of (C-H3)3SB11H14.-To an aqueous solution of NaB11H14, prepared as described in Example 1(B), is added an aqueous solution of trimethylsulfonium iodide, (CH3)3SI. A yellow precipitate forms, which is ltered from the reaction mixture, dried and then recrystallized from water. The carefully recrystallized salt, which is (CH3)3SB11H14, is colorless. The infrared absorption spectrum obtained on this salt shows a sharp B-I-I peak at 4.0 microns, and (CH3)3S+ and BHHM- peaks coincident at 9.6 microns.

Another sample of (CH3)3SB11H14 is subjected to elemental analysis with the following results:

Analyss.-Calcd for (CH3)3SB11H14 (percent): B, 56.6; C, 17.2; H, 11.0; S, 15.3. Found (percent): B, 53.8; C, 17.6; H, 11.2; S, 15.5.

Example 6 Preparation of (C2H5)3NHB11H14.-To an aqueous solution of NaBuHM-Zjdioxanate is added an aqueous solution of triethylammonium chloride, (C2H5)3NHCI. The yellow precipitate that forms is ltered from the reaction mixture and dried. The dried salt, which is (C2H5)3NHB11H14, is recrystallized from water and the resulting crystals are colorless. The infrared absorption spectrum of the recrystallized product shows B-H absorption at 4.0 microns; N-H absorption at 3.15 microns, and BHHM" and (C2H5)3NH+ absorption coincident at 9.7 microns.

Analysis.-Calcd for (C2H5)3NHB11H14 (percent): B, 50.6; C, 30.7; H, 12.9; N, 6.0. M.W., 234. Found (percent): B, 49.7; C, 31.4; H, 13.5; N, 6.0. M.W., 231 (by boiling point elevation of ClCHgCHzCl).

The complete infrared absorption spectrum of a sample of (C2H5)3NHB11H14 recrystallized from a mixture of CHC13 and CH2C12, in a Nujol mull is shown in FIG. 2. In this spectrum the absorption peaks at 3.45, 6.9, and 7.3 microns are due to the NujoL There are significant differences in the absorption spectrum given by (C2H5)3NHB11H14 compared to the infrared absorption spectrum of (C2H5)3NHB10H13 which is shown in FIG. 3. The salt used for FIG. 3 was prepared by the method of Hawthorne et al., I. Am. Chem. Soc., 82, 1825 (1960) by addition of triethylamine to a benzene solution of decaborane. The (C2H5)3NHB10H13 used for infrared analysis was a sample recrystallized from chloroform and the infrared determination was made in Nujol mull. As in the case in FIG. 2, the absorption peaks in FIG. 3 at 3.4, 6.85, and 7.3 microns are due to the NujoL Comparison of FIGS. 2 and 3 shows significant differences in the absorption spectrum for the BHHM* salt in comparison with that of the BH13 salt. In particular, signicant absorption peaks of the B10H13 salt which are cornpletely absent from the BHHM* spectrum occur at 4.05, 5.2, 6.4, 6.75, 8.55, 9.25, 9.9, 10.6, 10.9, 11.4, 11.95, 12.3, 12.9, 13.4 microns. These absorption peaks are not present in the spectrum for the BHHM salt which is shown in FIG. 2.

The B11 magnetic resonance of (C2H5)3NHB11H14 is shown in FIG. 4. The B11 magnetic resonance is a sharp symmetrical doublet of about 140 c.p.s. separation displaced about 34 p.p.m. up-iield from the boron resonance frequency of trimethyl borate. This magnetic resonance spectrum of the BUHM'A salt is markedly different from the B11 magnetic resonance spectrum of shown in FIG. 5. The B11 magnetic resonance of the B10H13- salt is more complex. There is a broad unsymmetrical doublet of about 128 c.p.s. separation at +215 p.p.m. from the boron resonance frequency of trimethyl borate and a weaker but symmetrical and sharp doublet of 129 c.p.s. separation at +52 p.p.m. from trimethyl borate. Both of these nuclear magnetic resonance spectra are determined at 14.3 mc. on solutions of the polyhydropolyborate salts in methylene chloride.

Pure (C2H5)3NHB11H14 in methylene chloride solution exhibits no absorption maximum in ultraviolet light. In contrast to this, the (C2H5)3NHB10H13 salts of Hawthorne et al., J. Am. Chem. Soc., 82, 1825 (1960) show absorption maxima at 267 millimicrons (e=2500) and at 335 millimicrons (e=1730).

Example 7 Preparation of KB11H14.-An aqueous solution of one equivalent of potassium hydroxide is added to an aqueous solution of (C2H5)3NHB11H14 (prepared as in Example 6) and the resulting solution is evaporated to dryness. The solid residue obtained is KBHHM. The infrared absorption spectrum of this salt shows absorption due to B-H at 4.0 microns and absorption due to BHHM- at 9.65 microns.

Analyss.-Calcd for KBHHM (percent): B, 69.2; H, 8.2; K, 22.6. Found (percent): B, 67.2; H, 8.1; K, 21.7.

Example 8 Preparation of RbB11H14.-An aqueous solution of one equivalent of rubidium chloride is added to an aqueous solution of NaBnHM, prepared as described in Example 1(B). A yellow precipitate is formed and this is ltered from the reaction mixture. After recrystallizing from water, the RbB11H14 is colorless. The infrared absorption spectrum exhibited by this rubidium salt shows B-H absorption 4.0 microns, and BHHM- at 9.55 and 9.85 microns.

Analysis.-Calcd for RbBnH14 (percent): B, 54.4; H, 6.5; Rb, 39.1. Found (percent): B, 52.8; H, 6.6; Rb, 36.3.

8 Example 9 Preparation of (CH3)3NHB11H14.-An aqueous solution of one equivalent of trimethylammonium chloride, (CH3)3NHC1, is added to an aqueous solution of NaBuHM, prepared as described in Example 1(B). A yellow precipitate of (CH3)3NHB11H14 forms and this is removed from the reaction mixture by filtration. On recrystallization of the yellow precipitate from water a colorless precipitate of (CH3)3NHB11H14 is obtained. The infrared absorption spectrum obtained on this recrystallized product shows B-H absorption at 4.0 microns, BHHM at 9.7 at 9.7 and 9.9 microns, N-H absorption at 3.15 microns, and (CH3)3NH+ at 10.3 microns.

Analysz's.-Calcd for (CH3)3NHB11H14 (percent): B, 61.7; C, 18.6; H, 12.5; N, 7.2. Found (percent): B, 61.6; C, 16.8; H, 12.6; N, 7.5.

The examples have illustrated the formation of certain specific salts of the BHHM- anion. However, the products of this invention include any salt of the BHHM- anion with any metal having an oxidation potential of at least 0.5 volt and an atmoic number less than 57, ammonium, sulfonium or phosphonium cation. Thus, when the procedure of Examples 1 and 2 are repeated with 'the sodium and lithium borohydrides of those examples replaced by potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium and barium borohydrides, the corresponding potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium and barium salts of the BHHM* anion are produced. These salts are isolated as the etherates of the particular ethers employed as reaction medium in their preparation, or as the dioxanates (which are formed by the procedure described in Example 2).

When the cesium chloride of Example 4 is replaced by any other Water-soluble non-oxidizing salt of cesium, e.g., a bromide, iodide or acetate, and the procedure for Example 4 is repeated, the cesium salt of the BHHM- anion is obtained.

Likewise, when the tetramethylammonium chloride of Examples 1(C) and 3, the triethylammonium chloride of Example 6, the trimethylammonium chloride of Example 9, and the trimethylsulfonium iodide of Example 5 are replaced by di-, tri-, or tetraalkylammonium halide, a trialkylsulfonium halide or a tetraalkylphosphonium halide and the procedures of those examples followed the corresponding substituted ammonium, sulfonium and phosphonium salts of BHHM- are obtained. For example, specific ammonium salts obtained in this way include diethylammonium, tri-n-propylammonium, tetraisobutylammonium, dioctylammonium, tetradecylammonium, and monooctadecylammonium salts of the BUHM* anion. Furthermore, other specific sulfonium salts that are obtained include triethyl, triisopropyl, trihexyl-, and tridecylsulfonium salts of the BHHM* anion. Specific phosphonium salts of the BHHM anion obtained in the above mentioned manner include tetramethylphosphonium, tetraethylphosphonium, and tetraoctylphosphonium salts of the BHHM- anion.

Finally, specific water-soluble salts of the BUHM- anion that can be prepared by the metathetical reaction described hereinbefore include the aluminum, chromium, zinc, manganese and zirconium salts of B11H14.

The salts of this invention are useful in various applications. Thus, the ethereal or aqueous solutions of these salts are useful reducing agents. For example, such solutions reduce silver or nickel salts to the free metals.

The salts are also stable towards alkali, consequently making them useful as reducing agents in alkaline systems.

Furthermore, the salts of this invention are useful as components as high energy fuels. These salts are ignited by treatment with concentrated nitric acid and the compounds burn rapidly.

The compounds of this invention are generically useful as components of fireworks compositions to impart a pleasing color and sparkle to the display. Every one of the compounds of the invention contains an anion which has boron as a common component. The presence of this element imparts a green color to a reworks, rocket or iiare display. The compounds of this invention can have a wide range of metal cations and it is thus possible to provide a broad range of colors in any display or ilare by appropriate choice of cation. The compounds of the invention can be used in combination with oxidizing agents, e.g., lithium perchlorate, sodium nitrate, potassium permanganate, strontium peroxide, manganese dioxide, and the like to provide the desired propulsion effect and color.

The salts of the BHHM- anion are useful as a source of hydrogen. The hydrogen of this anion is liberated quantitatively on hydrolysis in the presnece of a catalyst such as platinum black. The complete hydrolysis of the BHHM salts can be effected in aqueous hydrochloric acid in the presence of platinum black. The nal supernatent liquid obtained in such hydrolysis systems is non-reducing toward silver nitrate, showing that hydrolysis is complete. In a typical experiment, 0.8023 g. Of (C2H5)3NHB11H14 iIl a. Platinum Weighing iS placed in a sidearm of a reaction vessel containing 0.1 g. of platinum black and 20 milliliters of 4 N aqueous hydrochloric acid which is then cooled to 196 C. and the reaction vessel is evacuated to less than 1 micron. The aqueous acid is then allowed to melt and the sample is dislodged into the acid. Hydrogen evolution is qrapid at room temperature. The volume of the system is such that on complete hydrolysis the total pressure approaches but does not exceed 760 millimeters. The reaction mixture is heated to reux until the pressure remains unchanged over a period of to 30 minutes. The hydrolysis mixture is cooled to 196 C. and the gas which has been generated is passed through a liquid nitrogen and transferred to a known volume with a Tpler pump. Triplicate experiments give 2305.5, 2301.5 and 2297.3 (average 2301.4) cc. of hydrogen per gram of triethylammonium tetradecahydroundecaborate. This is within 0.75% of the 2284.4 cc./g. required for (C2H5)3NHB11H14 calculated in accordance with the following equation:

BnHMhf-i- Boi-*i- The quantitative measurement of the hydrogen evolved on complete hydrolysis of purified BHHM" salts conrms the BHHM- formulation. In contrast, complete hydrolysis of B10H13- salts would proceed in accordance with the following equation:

Thus, the theoretical quantity of hydrogen that would be evolved from one `gram of (C2H5)3NHB10H13 is 2210 cc.

The foregoing detailed description has been given for clearness of understanding only and no unnecessary limitations are to be understood therefrom. The invention is not limited to the exact details shown and described, for obvious modifications will occur to those skilled in the art.

The embodiments of the invention in which an exclusive property or privilege is claimed are deiined as follows:

1. A compound of the formula wherein M is a cation having a valence of 1-4 selected from the group consisting of metals having a standard oxidation potential of at least 0.5 volt and an atomic number less than 57 selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, barium, aluminum, scandium, titanium, vanadium, chromium, manganese, zinc, gallium, yttrium, zirconium' and niobium, and n, the valence of the radical M, is an integer greater than 0 and less than 5.

2. An aqueous solution of NaBnHM.

3. An aqueous solution of KBHHM.

4. A SOlld hydrate 0f NaBuHM.

5. CSB11H14.

References Cited UNITED STATES PATENTS 6/ 1967 Miller et al. 23-358 OTHER REFERENCES MILTON WEISSMAN, Primary Examiner U.S. C1. X.R.

P04050 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION meno No. ,772,ll26 narod November 13, 1973 Inventeurs) Victor D. Aftandlian It is certified that error appears in the above-identified patent :md that said Letters Patent are hereby corrected as shown below:

F- l l1 Col. 7, line 56 .-v "B1 should be "B o Col. 9, line 28'- correctrspelling of "rapid". Rewrite the claims as follows: Z'. A compound of the formula o and less than 5] [2 3] An 'queous solution of ITaLIBllI-lq. I A [3 7 An aqueous solution of KB:L:'LH]

L "l+ 7 A sono hydrate of NaBllHlu.

LLL ["5] CsBllHla.

end l:sealed this 16th day of April l'ftt.

(SEAL) Attest:

EDWARD I-LFLJLTGHER5JR. MARS-ALL DANN Atestng Officer*` Gommissoner of Patents 

